pSilencer 5.1 Retro vectors harness retroviruses’ ability to stably integrate into the host genome of nearly all mitotically active cells and include a puromycin resistance gene for selection of cells that express the recombinant DNA. The pSilencer 5.1 Retro vectors enable researchers to study the long-term effects of reducing the expression of specific genes in cell culture models. This technology expands the capabilities of RNA interference research to address long-term alteration of gene expression.